The present invention relates to a raster position adjusting circuit for controlling a horizontal raster position of an electromagnetic type cathode ray tube (which will be referred hereinafter to as a CRT).
FIG. 1 is an illustration of an arrangement of a conventional raster position adjusting circuit including a first power source Vcc1 designated at numeral 1 and a second power source Vcc2 designated at numeral 2, the first power source Vcc1 being for the circuit and the second power source Vcc2 being for supplying a direct current to a horizontal deflecting coil 9. The horizontal raster is made by supplying a direct current to the horizontal deflecting coil 9 and the horizontal right and left raster position adjustment can be effected by means of current path systems indicated by arrows A (chain line) and B (dotted line) in FIG. 1. The horizontal deflection circuit is basically composed of the first power source Vcc1, a constant-voltage source 3, a flyback transformer 8, the horizontal deflecting coil 9, a direct-current blocking capacitor 10, and a horizontal output circuit 11, and additionally equipped with a choke coil 12 (which prevents the horizontal pulse from being by-passed), resistors 6, 7, transistors 4, 5, a control 13 and the second power source Vcc2 in order to change the raster position. A partial voltage of the second power source Vcc2 due to the position of a movable contact of the control 13 is applied to the bases of both the transistors 4 and 5 whereby either the transistors 4 and 5 turns ON in accordance with the applied voltage due to the volume 13 in relation to the same emitter electric potential so as to supply a current to the horizontal deflecting coil 9 through the current path system indicated by the arrow A or B.
There is a problem which arises from such a conventional raster position adjusting circuit using the control 13, however, in that there is the possibility of lowering its reliability due to an imperfect connection of the movable contact because the control 13 has a mechanical structure, and difficulty is encountered to easily achieve the automization of the adjustment of the raster position in the manufacturing process because of requiring a dedicated device for operation of the control. In addition, the position for the provision of the control is restricted on the printed circuit board.